This invention is directed to a method for the thin-layer chromatographic separation of enantiomers of the general formula ##STR3## in which C* represents an asymmetry center and the substituents R.sup.1, R.sup.2, and R.sup.3 are such that they provide the structural element ##STR4## for .alpha.-amino- or .alpha.-iminocarboxylic acids or for a derivative of such carboxylic acids, either of which contains no free thiol groups, by means of ligand exchange to a chiral stationary phase.
It is known that enantiomers can be separated by high-pressure liquid chromatography (HPLC) on a chiral stationary phase and the preferred method is the ligand exchange chromatography method as reviewed by W. Lindner [Chimia, 35, 294 (1981)]. However, these HPLC separation methods have the disadvantage of requiring relatively expensive and troublesome apparatus as well as considerable time to prepare and execute the separation. They are therefore less suitable for routine analysis and especially for process control.
It is an object of this invention to provide a simplified method for the separation of enantiomers of the general formula (I) and in particular to provide a simple method that can be carried out quickly and is suitable for process or plant control, for example, purity assays.